A bis-porphyrin compound (VC7) has been used as a donor along with two acceptors, namely, PC 71 BM and IT-4F (non-fullerene), for the production of efficient all-small-molecule ternary organic solar cells (OSCs), and their performance has been compared with that of the binary counterparts. After optimization of the ternary blend VC7:PC 71 BM:IT-4F (1:0.3:0.9), organic solar cells showed an overall power conversion efficiency (PCE) of 15.08% (J SC = 23.74 mA/cm 2 , V OC = 0.87 V, and FF = 0.73), which is higher than the values obtained for the binary counterparts, i.e., 9.39 and 11.61% (J SC = 21.94 mA/cm 2 , V OC = 0.84 V, and FF = 0.63) for VC7:PC 71 BM and VC7:IT-4F, respectively. The improvement in the PCE for the ternary OSC is a consequence of the increase in the three parameters, V OC , J SC , and FF. The growth in the V OC value is associated with the upshifted LUMO level of PC 71 BM as compared to IT-4F. The increase in the J SC value is attributed to the higher exciton generation rate, which is associated with the effective utilization of excitons due to the broader absorption profile and energy transfer between the two acceptors (PC 71 BM to IT-4F). The higher FF value of the ternary OSCs is related to the more balanced charge transport and the reduced bimolecular and trap-assisted recombination, as evidenced by the increased charge carrier lifetime and low charge extraction time.

Despite their minimal HOMO energy level offset promising power conversion efficiencies up to 13.54% have been recorded for ternary organic solar cells using coumarin-based molecular donors and fullerene-free acceptors.

A new non-fullerene small molecule acceptor (MPU6) containing a diketopyrrolopyrrole (DPP) acceptor unit as core, connected to dicyanomethylene-3-ethylrhodanine end-capped units via thienylethynylselenophene bridges, has been designed and synthesized and its...

An electron acceptor in a bulk heterojunction (BHJ) is one of the significant factors for the performance of organic solar cells (OSCs). Acceptors are required to possess an appropriate energy level to be well fitted with donors and a complementary absorption profile in the near-infrared (NIR) region of solar spectra. Herein, two novel star-shaped electron acceptors TBT-1 and TBT-2 denoted as 3a and 3b, respectively, based on a planar truxene core conjugated with three 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) units were designed. Both 3a and 3b show strong absorption in both visible and NIR regions in solution and in films. Due to the strong electron-donating capability of the dimethylamino group and a good π-conjugative effect, 3a displays a slightly higher highest occupied molecular orbital (HOMO) level (−5.40 eV) and a deeper lowest unoccupied molecular orbital (LUMO) level (−3.96 eV) compared to 3b (HOMO = −5.52 eV and LUMO = −3.94 eV), resulting in red-shifted absorption, showing a narrower optical band gap of 1.44 eV than that of 3b (1.58 eV). When blended with a donor polymer P, the OSCs based on P:3a and P:3b exhibit a superior short-circuit current density (J sc ), high electron mobility, and open-circuit voltage (V oc ). OSCs based on optimized P:3a and P:3b exhibit the best power conversion efficiency (PCE) values of 13.41 and 11.75%, respectively. To the best of our knowledge, this is among the best values for OSCs with a non-fullerene small-molecule acceptor (NFSMA) based on BODIPY derivatives. These outcomes suggest that integrating extended conjugation into a star-shaped building block encourages designing high-performance NFSMAs for application in OSCs.

The emergence of nonfullerene small-molecule acceptors (NFSMA) with the advantages of synthetic versatility, high absorption coefficient in wide wavelength range, and high thermal stability has attained the power conversion efficiency (PCE) exceeding 19% for resulted organic solar cells (OSCs) with the optimization of interface engineering and active layer morphology. Interfacial layers including both hole transporting layer (HTL) and electron transporting layer (ETL) are equally important in the OSCs for facilitating electron and hole extraction from the bulk heterojunction (BHJ) photoactive layer by the respective electrodes. In this Review, we summarize the recent progress in the materials used as HTL and ETL in conventional and inverted OSCs on the basis of their effect on the PCE. Finally, the prospects of HTL and ETL materials for NFSMA-OSCs will be provided.