Combining the major problem of the world in terms of the global warming due to the greenhouse gases that implies the need of renewable clean energy and the progress in electronics the new recent direction in electronics seeks to develop methods and materials that can: (i) offer a feasible alternative source of clean renewable energy based on solar radiation (ii) enable high performance of the devices and (iii) sustain mechanical deformation.
The present project proposes a new type of organic flexible hybrid solar cell, combining the properties of both, organic material and silicon for low-cost organic photovoltaic devices. The proposed structure type is consisting in an elastomeric solar cell based on: thin truncated conical Si patterns incorporated in a donor/acceptor blend between the two transparent, flexible, metallic electrodes.
The main objectives of the project are the following:
(1) Realization of the truncated Si inverted nano-cones;
(2) Deposition of the organic materials above the Si inverted nano-cones;
(3) Elastomeric embedding of the obtained structure and substrate detachment;
(4) Front and rear electrode contact deposition and characterization of the structures.
The addressed methodology will imply the nanoimprint technology for truncated cones-patterning, matrix assisted pulsed laser evaporation for the organics, spin-coating for the PEDOT:PSS and electrospinning for the deposition of the metallic electrodes.

Dr. Oana Rașoga
Dr. Anca Stănculescu
Dr. Marcela Socol
Dr. Marius-Andrei Avram
Dr. Carmen Breazu
Dr. Gianina Popescu-Pelin
Dr. Alexandru Evanghelidis
Dr. Loredana Văcăreanu
Drd. Gabriela Petre
Tech. Maria Rădulescu

Stage I: Realization of truncated silicon nanocones (4.01.2021-31.01.2021)

Stage summary

During the stage 04.01.2021 - 31.12.2021, 6 activities were established, respectively: (1) Activity 1.1: Realization of patterns by UV-NIL and synthesis of organic materials. Within this activity, structures were made using the lithographic printing technique. A beautiful collaboration was also created with those from EVG (Austria) who also contributed to the achievement of the results. Two types of working masks were used and also purchased another two. The desired oligomers were synthesized and tested for the use in solar cell structures. (2) Activity 1.2: Wet or dry corrosion of patterned substrates in order to obtained silicon patterns. This activity complements the previous one, consisting in the transfer of the patterns into the silicon layer. For this purpose, dry corrosion was carried out at cryogenic temperatures as well as wet corrosion using different types of solutions such as: Piranha, Royal water, aqueous HF solution and KOH solution. (3) Activity 1.3: Characterization of the truncated nanocones patternes by SEM, AFM, FTIR, synthesized organic materials and a characterization of the initial structures. In this activity, the results of the previous activities were highlighted, through SEM, FTIR or AFM analyzes in order to see what needs to be improved / optimized in the manufacturing processes. (4) Activity 1.4: Optimization of the paterning and chemical etching processes; Following the results obtained in the characterization of the samples, the parameters of the nanoimprint process were improved by establishing the optimal spincoating parameters, an attempt was made to optimize wet etching processes by testing different solutions or concentrations. (5) Activity 1.5: Characterization of optimized nanopaterns by SEM, AFM, FTIR. In this activity, the structures previously obtained through the related techniques were analyzed. In addition, classical structures for photovoltaic applications have been developed in order to test the synthesized oligomers as well as other substances. (6) Activity 1.6: Dissemination of the results obtained for the classic structure as well as the creation of the WEB page. This activity was strictly related to the presentation of the results of the whole team, following as requested by the project evaluators for the project director to improve his CV in terms of oral presentations at conferences. Therefore, the PhD student in the project had a poster presented at EMRS Spring, and the project director two oral presentations at EMRS Fall and CAS 2021. The effort to disseminate the results was a team effort and not only, proven by the papers submitted or accepted.

Stage II: Deposition of organic materials on top of inverted truncated nanocones silicon patterns

Stage summary

During the stage: 01.01.2022 – 31.12.2022 5 activities were established, as follows: (1) Activity 2.1: Optimization of dry etched processed and truncated nanocons passivation, a surface treatment (end of Task 1.3 and 1.4). During this activity, solar cell structures were realized onto the etched substrates for last year. After the analyzes it resulted that the recipe: cryogenic etching + wet etching with KOH can be utilized to obtain Si patterns that can contribute to enhance the solar cells parameters. The passivation has been realized by deposition of the conductive polymer onto the patterns. (2) Activity 2.2: Deposition of the PEDOT: PSS (task 2.2) and organic materials above silicon nanopatterns by spincoating (task 2.4); This activity comes to complete the former activity and consists in the deposition of the PEDOT: PSS as well as of the organic materials by spincoating. For the PEDOT: PSS deposition, two recipes have been chosen after prior test. These recipes have been used in function of the structure type upon which the deposition has been made. Moreover, two types of PEDOT: PSS have been utilized – HTL100 and PH1000. The organic materials have been deposited by spincoating on flat substrates in order to test the classical structures. Next year, the spincoating deposition of the organic materials onto Si nanopatterns will be done.  (3) Activity 2.3: Deposition of the organic materials onto silicon nanopatterns by MAPLE technique (task 2.3). During this activity, different synthetized/commercial organic materials have been deposited. Different types of concentrations were used for "frozen targets" as well as 3 deposition recipes.  (4) Activity 2.4: Characterization of the organic thin films deposited onto the Si nanopatterns from the morphological, topographical, crystallinity and optical properties point of view (task 4.2). Within this activity the organic films deposited by MAPLE technique have been characterized by means of the related techniques – FTIR, SEM, AFM, reflectance measurements, UV-VIS and photoluminescence. More, I-V characteristics of the resulted solar cells structures have been done. (5) Activity 2.5: Dissemination od the results obtained in Stage II, WEB page update. This activity is strictly connected with the results presentation of all the team members. Therefore, this year were 3 oral presentations at international conferences: EMRS Spring meeting 2022 – 2 presentations, META 2022 – 1 presentation. The PhD student within the project presented the most important results obtained using Si nanopatterns through a poster at the International Conference on Laser, Plasma and Radiation – Science and Technology. The effort put into disseminating the results was a team effort and not only, proven by the papers sent or accepted for publication

Stage III: Embedding the structure in the elastomer, detachment of the substrate (Objective 3) and deposition of the back and front electrodes, as well as the characterization of the obtained structures (Objective 4) (01.01.2023-31.12.2023)

Activity 3.1: Realization of the front electrode (front electrode) by electrospinning using a mixture of Ag nanoparticles and polyurethane, (b) Ag nanowires and (c) Ag nanoparticles and reduced graphene oxide – task 3.1. As part of this activity, recipes for electrospinning were performed and tested using different concentrations for polyurethane but also for added nanoparticles. Following the results obtained, recipes and solutions were sought regarding the manufacture of the electrode by electrospinning replacing the materials used. Activity 3.2: Elastomeric embedding of patterns and their detachment (Task 2.5); In this activity, different recipes for embedding and detaching patterns using PDMS were tried. The same material being used to encapsulate the cells.  Activity 3.3: Realization of the back electrode (rear electrode) by depositing thin layers of metals and later by electrospinning – Task 3.2; In this activity, different thin layers of metals were deposited and an attempt was made to make electrodes by electrospinning similar to activity A3.1  Activity 3.4: Encapsulation of the structure in elastomers (task 3.3). In this activity, it was attempted to embed the entire structure in PDMS, using a polymer sensitive to UV radiation as a bonding material. Activity 3.5: I-V characteristics of the structure (task 4.3). This activity consisted in tracing the I-V characteristics of organic cells on both flexible and rigid support using both electrodes made by deposition using the PLD or vacuum evaporation technique and by electrospinning or combined. Depending on the results obtained in the previous steps. It should be noted that this activity was also carried out in the previous years. Activity 3.6: Dissemination of the results obtained in stage III, update WEB page. This activity was strictly related to the presentation of the results of the whole team. Thus, there were 2 presentations at international conferences: CAS 2023 (poster) and ICPAM–15 (poster). The effort put into disseminating the results was a team effort and not only proven by the papers submitted or accepted for publication.

Flexible organic solar cell

Year 2021

Conferences:
(i) ”Organic heterostructures with indium-free transparent conductor electrode for opto-electronic applications” -Poster , authors: G. Petre, A. Stanculescu, M. Girtan, M. Socol, C. Breazu, L. Vacareanu, M. Grigoras, N. Preda, O. Rasoga, F. Stanculescu, (speaker Gabriela Petre) at E-MRS 2021 Spring Meeting Conference;
(ii) ” Effect of Aluminum nanostructured electrode on the properties of bulk heterojunctions based heterostructures for electronics”, oral presentation, authors: O. Rasoga, C. Breazu, M. Socol, A.-M. Solonaru, L. Vacareanu, G. Petre, N. Preda, A. Stanculescu, F. Stanculescu, G. Socol, M. Girtan, A. Doroshkevich; (speaker Oana Rașoga) at E-MRS 2021 Fall Meeting Conference;
(iii) ” Wafer-level fabrication of nanocones structures by UV-nanoimprint and cryogenic deep reactive ion process”, oral presentation, authors: Oana Rasoga, Christine Thanner, Olga Semenova, Andrei Marius Avram, Luiza-Izabela Jinga; (speaker Oana Rașoga) at CAS 2021 Conference .

Scientific papers:
1. Petre, G., Stanculescu, A., Girtan, M., Socol, M., Breazu, C., Vacareanu, L., Preda, N., Rasoga, O., Stanculescu, F. and Doroshkevich, A.S. (2022), Organic Heterostructures with Indium-Free Transparent Conductor Electrode for Optoelectronic Applications. Phys. Status Solidi A 2100521. https://doi.org/10.1002/pssa.202100521;
2.Stanculescu, A.; Socol, M.; Rasoga, O.; Breazu, C.; Preda, N.; Stanculescu, F.; Socol, G.; Vacareanu, L.; Girtan, M.; Doroshkevich, A.S. Arylenevinylene Oligomer-Based Heterostructures on Flexible AZO Electrodes. Materials 2021, 14, 7688. https://doi.org/10.3390/ma14247688
3.O. Rasoga, C. Thanner, O. Semenova, A. M. Avram and L. -I. Jinga, "Wafer-level fabrication of nanocones structures by UV-nanoimprint and cryogenic deep reactive ion process," 2021 International Semiconductor Conference (CAS), 2021, pp. 39-42, doi: 10.1109/CAS52836.2021.9604179.

Year 2022

Anul 2022
Conferences:
(i)  ”MAPLE deposited organic thin films based on P3HT and PC70BM on nanopatterned substrate”, - oral prezentation, authors: M. Socol, N. Preda, C. Breazu, G. Petre, A. Stanculescu, A. Stochioiu, G. Socol, S. Iftimie, C. Thanner, O. Rasoga; presented by Oana Rașoga at E-MRS 2022 Spring Meeting conference – on-line;
(ii) ”Flexible bulk heterojunction with non-fullerene acceptor deposited by MAPLE”- oral prezentation,  authors: A. Stanculescu, M. Socol, C. Breazu, O. Rasoga, G. Petre, G. Socol, G. Popescu-Pelin, N. Preda, L. Vacareanu, M. Girtan, F. Stanculescu; oral prezentation presented by Carmen Breazu at E-MRS 2022 Spring Meeting conference – on-line;
(iii)  ” MAPLE deposited organic thin films based on synthetized oligomers and PC70BM on silicon nanopatterned substrate” - poster, authors G. Petre, M. Socol, C. Breazu, A. Stanculescu, G. Popescu-Pelin, G. Socol, S. Iftimie, S. Antohe, L. Vacareanu, C. Thanner, O. Rasoga, presented by Gabriela Petre at International Conference on Laser, Plasma and Radiation – Science and Technology – București.
(iv) Prezentare orală intitulată” Nanopatterned substrates for application in organic photovoltaic cell structures”, oral prezentation, authors: C. Breazu, O. Rasoga, A. Stanculescu, M. Socol, G. Popescu-Pelin, G. Petre; presented by Carmen Breazu at META 2022 conference- Spania;

Scientific papers:
(i) ”Effect of Aluminum Nanostructured Electrode on the Properties of Bulk Heterojunction Based Heterostructures for Electronics”, Rasoga, O.; Breazu, C.; Socol, M.; Solonaru, A.-M.; Vacareanu, L.; Petre, G.; Preda, N.; Stanculescu, F.; Socol, G.; Girtan, M.; Stanculescu, A. Nanomaterials 2022, 12, 4230. https://doi.org/10.3390/nano12234230 - publicat online
(ii) ”Effects of solvent additive and micro-patterned substrate on the properties of thin films based on P3HT:PC70BM blends deposited by MAPLE”, Marcela Socol, Nicoleta Preda, Carmen Breazu, Gabriela Petre, Anca Stanculescu, Ionel Stavarache, Gianina Popescu-Pelin, Andrei Stochioiu, Gabriel Socol, Sorina Iftimie, Christine Thanner and Oana Rasoga – în evaluare la jurnaul Materials

Book Chapter:
(i) Pulsed Laser Deposition of Transparent Conductive Oxides on UV-NIL Patterned Substrates for Optoelectronic Applications, Socol, M. , Preda, N. , Breazu, C. , Rasoga, O. , In: Yang, D. , editor. Thin Film Deposition - Fundamentals, Processes, and Applications [Working Title] [Internet]. London: IntechOpen; 2022 [cited 2022 Nov 28]. Available from: https://www.intechopen.com/chapters/82539 doi: 10.5772/intechopen.105798

Year 2023:

Conferences:

(i) ” Effects of the Micro-Patterned Substrate on the properties of thin films based on different organic blends deposited by MAPLE for photovoltaic applications”,  Rasoga, C. Thanner, C. Breazu, G. Petre, M. Socol, G. Popescu-Pelin, S. Iftimie, A. Stanculescu,  CAS 2023-România

(ii)  „Investigation of the properties of some binary and ternary layers obtained by MAPLE for optoelectronic applications”,  Breazu, A. Stanculescu, O. Rasoga, G. Socol, G. Popescu-Pelin, G. Petre, M. Socol,  ICPAM-15, 2023-România;

Scientific papers:

(i) ”Organic heterostructures based on thermal evaporated phthalocyanine and porphyrin as mixed (ZnPc:TpyP) or stacked (ZnPc/TpyP) films”, G. Petre, M. Socol, N. Preda, C. Breazu, O. Rasoga, F. Stanculescu, A. Costas, S. Antohe, S. Iftimie, G. Socol, A. Stanculescu, Thin Solid Films (2023), 87, 140140 , https://doi.org/10.1016/j.tsf.2023.140140 -online.

(ii)”Perylene diimide derivative based binary and ternary layers obtained by a laser technique for optoelectronic applications", C. Breazu, A. Stanculescu, O. Rasoga, N. Preda, A. Costas, A. M. Catargiu, G. Socol, G. Popescu-Pelin, A. Stochioiu, S. Iftimie, G. Petre, M. Socol, trimis la Optics and Laser Technology manuscript number: JOLT-D-23-02301 (în evaluare).

(iii)” MAPLE deposition of reduced graphene oxide for multilayer transparent conductive electrodes” M. Socol, N. Preda, A. Costas, A. Stanculescu, O. Rasoga, I. Stavarache, G. Petre, G. Popescu-Pelin, I. Jinga, C. Breazu și G. Socol, trimisă spre publicare în Nanomaterials

(iv) ”Induced effects of nano-patterned anode on the electrical and photo-electrical properties of PTB7-Th:ICBA (1:1, wt.%) heterojunction”, Tudor Suteu, Vlad-Andrei Antohe, Stefan Antohe, Ionel Stavarache, Maria Cristina Balasin, Gabriel Socol, Marcela Socol, Oana Rasoga, Sorina Iftimie, trimisă spre publicare in APL Materials, manuscript number  #APM23-AR-01046.

Submit patent application:

(i)Procedeu de realizare a unor structuri de celule fotovoltaice flexibile si impermeabile pe bază de strat tampon texturat de siliciu amorf dopat p și materiale organice, elaborat de: Marcela Socol, Oana Rașoga, Sorina Iftimie, Claudiu Ciubotaru, Carmen Breazu, Ionel Stavarache, Gabriel Socol, Anca Stănculescu, Gianina Popescu-Pelin, număr înregistrare A 2023 00776.