Different Morphology Dependence for Efficient Indoor Organic Photovoltaics: The Role of the Leakage Current and Recombination Losses

Abstract

Efficient indoor organic photovoltaics (OPVs) have attracted strong attention for their application in indoor electronic devices. However, the route to optimal photoactive film morphology toward high-performance indoor devices has remained obscure. The leakage current dominated by morphology exerts distinguishing influence on the performance under different illuminations. We have demonstrated that morphology reoptimization plays an important role in indoor OPVs, and their optimal structural features are different from what we laid out for outdoor devices. For indoor OPVs, in order to facilitate low leakage current, it is essential to enhance the crystallinity, phase separation, and domain purity, as well as keeping small surface roughness of the active layer. Furthermore, considering the reduced bimolecular recombination at low light intensity, we have shown that PM6:M36-based indoor devices can work effectively with a large ratio of the donor and acceptor. Our work correlating structure–performance relation and the route to optimal morphology outlines the control over device leakage current and recombination losses boosting the progress of efficient indoor OPVs.

High‐Performance Green Thick‐Film Ternary Organic Solar Cells Enabled by Crystallinity Regulation

“…The dark current is usually dominated by the leakage current at low bias voltage, where the leakage current originates from the carrier recombination generated by the traps/defects in the blends. [ 56 ] Figure 2d shows the dark current density versus voltage of Y6‐based and CH1007‐based ternary thick‐film devices. The dark current density of CH1007‐based ternary thick‐film devices is an order of magnitude lower than that of Y6‐based devices, indicating less trap in PM6:BTR‐Cl:CH1007 active layer.…”

High‐Performance Indoor Organic Solar Cells Based on a Double‐Cable Conjugated Polymer

“…However, there are limited research efforts that have been devoted to the material design and device optimization for indoor OSCs compared with their well‐developed outdoor counterparts. [ 3,6 ]…”

“…[ 7 ] However, these materials are not very appropriate for indoor operations, as the emission spectra (Figure 1) of most indoor light sources such as fluorescent lamps, light‐emitting diodes (LEDs), and so on, are located in the visible light region. In addition, the demands for crystallinity and phase separation of the photoactive films are also different for indoor and outdoor PV [6a,8] . To obtain high‐performance indoor OSCs, the photoactive materials, film morphology, and interfacial contacts should be carefully designed and optimized [3b,9] .…”

“…[ 13 ] Moreover, the lowered J SC will generate additional energy loss, resulting in lower open‐circuit voltage ( V OC ) compared with outdoor PV [8b,14] . According to Equation S1, S2, Supporting Information, the dark currents of indoor PV cells should be minimized to achieve higher V OC as the photocurrents become very low under indoor light [6a] . Hence, the indoor OSC devices should have minimized leakage (dark) currents, suppressed trap‐mediated charge recombination, and acceptable energy loss.…”

Over 31% efficient indoor organic photovoltaics enabled by simultaneously reduced trap-assisted recombination and non-radiative recombination voltage loss

“…This is one of the key reasons why the LBL indoor device obtains a significantly higher FF than that of the BHJ indoor device. We speculated that the strong crystallinity, large and pure domains (less boundaries for leakage) 46 and ideal interface contact all contribute to the low leakage current of the LBL device. To distinguish the leakage current of the bulk phase and interface is beyond the scope of this work.…”