Organic solar cells (OSCs) are an alternative photovoltaic technology with a promising potential for a cost-effective, clean and sustainable source of energy. The performance of the solution-processable fullerene-based OSCs has been extensively investigated. However, the weak absorption in the long wavelength range, limited electronic property tuning capability and expensive purification processes are some of the limiting fac-Remarkable progress has been made in the development of high-efficiency solution-processable nonfullerene organic solar cells (OSCs). However, the effect of the vertical stratification of bulk heterojunction (BHJ) on the efficiency and stability of nonfullerene OSCs is not fully understood yet. In this work, we report our effort to understand the stability of nonfullerene OSCs, made with the binary blend poly[(2,6-(4, 8-bis(5-(2-ethylhexyl) thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′] dithiophene-4,8-dione)] (PBDB-T):3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2b:5,6-b′] dithiophene (ITIC) system. It shows that a continuous vertical phase separation process occurs, forming a PBDB-T-rich top surface and an ITIC-rich bottom surface in PBDB-T:ITIC BHJ during the aging period. A gradual decrease in the built-in potential (V 0 ) in the regular configuration PBDB-T:ITIC OSCs, due to the interfacial reaction between the poly(3,4ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole transporting layer and ITIC acceptor, is one of the reasons responsible for the performance deterioration. The reduction in V 0 , caused by an inevitable reaction at the ITIC/PEDOT:PSS interface in the OSCs, can be suppressed by introducing a MoO 3 interfacial passivation layer. Retaining a stable and high V 0 across the BHJ through interfacial modification and device engineering, e.g., as seen in the inverted PBDB-T:ITIC OSCs, is a prerequisite for efficient and stable operation of nonfullerene OSCs.

Ultraviolet (UV) organic optoelectronic devices have been attracting extensive research owing to their great potential in a variety of applications such as biological and chemical sensing, excitation lighting source, high-density...

The effect of 2-D photonic-structures on omnidirectional and broadband light absorption enhancement in organic solar cells (OSCs) is analysed using a combination of theoretical simulation and experimental optimization. The photonic structures in the active layer, with a blend system of poly[4,8-bis[(2-ethylhexyl)oxy] benzo[1,2-b:4,5-bA] dithiophene-2, 6-diyl][3-fluoro-2-[(2-ethylhexyl) carbonyl]thieno[3,4-b]-thiophenediyl] :[6,6]-phenyl-C70butyric-acid-methyl-ester (PTB7:PC70BM), were prepared by the nanoimprint method. It shows that the 2-D photonic structures enable not only broadband but also omnidirectional absorption enhancements in the PTB7:PC70BM-based OSCs over a broader angle range of the incident light, leading to >11 % increase in the power conversion efficiency, as compared to an optimal planar control cell. A weak angular dependency on light absorption is a unique feature of the photonic-structured OSCs, which is useful for different applications.

A significant enhancement in ultraviolet (UV) durable indium tin oxide (ITO)-free flexible nonfullerene organic solar cells (OSCs) has been demonstrated using a hybrid nanostructured flexible transparent electrode (FTE), comprising a mixture of 0D silver nanoparticles (AgNPs), 1D Ag nanowires (AgNWs) and 2D exfoliated graphene sheets. The FTE exhibits high optical transparency and electric conductivity, good air stability and full-solution fabrication capability at a low processing temperature. An average power convention efficiency (PCE) of 8.15% has been obtained for the flexible nonfullerene OSCs, based on the blend of poly[(2,6-(4, 8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thi enyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c'] dithiophene-4,8-dione)] (PBDB-T): 3,9bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dit hieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b'] dithiophene (ITIC). The flexible PBDB-T:ITIC OSCs exhibit an excellent UV durability compared to the ITO-based control cell, realized by the tailored FTE absorption in wavelength < 380 nm. The novel FTE developed in this work provides a promising alternative to ITO for use in UV durable flexible OSCs, serving as a UV filter to impede an unavoidable UV-induced degradation in ITO-based OSCs.

A comprehensive study on inverted organic solar cells (OSCs) with a moth’s eye nanostructured (MEN) active layer was carried out. Performance of the MEN-based OSCs and the corresponding control planar cells, fabricated with blend of poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-bA] dithiophene-2, 6-diyl][3-fluoro-2-[(2- ethylhexyl) carbonyl]thieno[3,4-b]-thiophenediyl] (PTB7):[6,6]- phenyl-C70- butyric-acid-methyl-ester (PC70BM) was analyzed. The efficiency of the MEN-based OSCs was optimized by adjusting the height of MEN pattern in the active layer. Our experimental and theoretical results reveal that the MEN pattern enhances light absorption in the PTB7:PC70BM active layer, especially over the long wavelength region. This leads to a 7.8% increase in short circuit current density and a 6.1% increase in power conversion efficiency over those of the control planar cell.