Optimization of PDTS-DTffBT-Based Solar Cell Performance through Control of Polymer Molecular Weight

Abstract

Herein, we investigated the effect of molecular weight (MW) on the efficiency of PDTS-DTffBT based polymer solar cells (PSCs). PDTS-DTffBTs with three different MWs were synthesized by controlling the polymerization conditions. The performance of PSCs improved significantly as the number-average molecular weight (M n) increased from 9 to 36 kDa. Combined with UV–vis absorption and electrochemical cyclic voltammetry measurements, the absorption properties and frontier orbital energy levels of the polymers were estimated, indicating the red-shifted light absorption and up-shifted highest occupied molecular orbital (HOMO) energy level when MW increased. PDTS-DTffBT with high MW also provided increased charge mobility, smoother film surface, and reduced domain size in morphology of the PDTS-DTffBT:PC71BM active layer. The performance of PDTS-DTffBT based PSCs was improved owing to these MW related properties, and both short circuit current density (J SC) and power conversion efficiency (PCE) went up significantly with increasing MW. The best PCE of 6.40% was achieved by the devices based on the PDTS-DTffBT with a M n value of 36 kDa.

Achieving an Efficiency Exceeding 10% for Fullerene‐based Polymer Solar Cells Employing a Thick Active Layer via Tuning Molecular Weight

“…Therefore, the M n could be easily affected by synthetic condition such as polymerization time, temperature, concentration, and so on . In recent years, a lot of reported works have demonstrated that the M n usually has great impact on the performance of PSCs via significantly affecting the molecular orientation, hole mobility, domain purity, and vertical composition profiles . However, a systemic study that clarifies the dependence of optimal thickness of active layer on polymer M n , which is of vital importance to develop a facile approach to realize high‐performance thick‐film PSCs, has not been made.…”

Enhanced open-circuit voltages and efficiencies: the role of oxidation state of molybdenum oxide buffer layer in polymer solar cells

“…In addition, to demonstrate the universal applicability of the air annealing method, we also used PDTS-DTffBT, which we reported before, 35,36 as polymer donor to fabricated PSCs and test the effect. The chemical structure of the materials and the J-V curves are showed in Fig.…”

Direct arylation polymerization toward a narrow bandgap donor–acceptor conjugated polymer of alternating 5,6‐difluoro‐2,1,3‐benzothiadiazole and alkyl‐quarternarythiophene: From synthesis, optoelectronic properties to devices

“…Such differences between E3a and Stille‐B1 in both OFETs and OPVs might be due to the end‐group effect present in polymers synthesized via Stille coupling (Fig. ), while other factors such as the polymer molecular weight and structural ordering might also play a role. The similar superior photovoltaic performance of phenanthridinone‐based conjugated polymers synthesized via DAP versus the same type of polymers synthesized via Suzuki coupling was also recently reported by Leclerc's group .…”