Non-fullerene organic solar cells based on thienopyrroledione comprising random copolymers; effect of alkyl chains


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Yaşa M., Depci T., Alemdar E. , Özdemir Hacioğlu Ş., Çırpan A. , Toppare L. K.

2 International Conference on Photovoltaic Science and Technologies, Ankara, Turkey, 30 November - 02 December 2020, pp.79-80

  • Publication Type: Conference Paper / Summary Text
  • City: Ankara
  • Country: Turkey
  • Page Numbers: pp.79-80

Abstract

Two new random copolymers, signed as P1 and P2, were designed and synthesized. 5-(2-ethylhexyl)-4Hthieno[

3,4-c]pyrrole-4,6(5H)-dione (TPD) was utilized as electron-accepting moiety whereas selenophene

was utilized as spacer, 4,8-bis[5-(2-ethylhexyl) thiophen-2-yl]-2,6-bis(trimethylstannyl)benzo[1,2-b:4,5-b’]

(BDT(TiC8)), thiophene and alkylthiophene were utilized as donor moieties. Structural analyses of the

polymers were carried out by attenuated total Reflectance-Fourier-transform infrared spectroscopy

(ATR−FTIR). Weight-average and number-average molecular weights (Mw, Mn) of the polymers were

determined via size exclusion chromatography (SEC). Electrochemical and spectroelectrochemical

measurements were performed to investigate optoelectronic properties. The polymers were used as

donor polymers in active layer to fabricate non-fullerene, bulk heterojunction (BHJ) organic solar cells

(OSCs). BHJ solar cells' device structure is ITO/PEDOT: PSS/Active Layer/LiF/Al, where active layer consists

of ITIC as acceptor and thienopyrroledione containing donors. Various optimization studies (solvent

selection, donor: determination of acceptor ratio, active layer’s mass ratio optimizations, determination

of the active layer's thickness, additive selection and thermal annealing) were carried out to obtain the

best performance from the devices. The device based on P1: ITIC (1:1) blend with a thickness of 161 nm

gave the best performance with a power conversion efficiency (PCE) of 7.94 %. The highest PCE obtained

from P2 based organic solar cell is 1.96 %. P2 exhibited low solubility attributed to the lack of alkyl groups

enhancing polymer solubility, electronic properties, and photovoltaic performances. Our study represents

a synthetic approach to exhibit alkyl chains' effect on OSCs' performance based on TPD containing random

polymers and non-fullerene acceptors.