For instance, in low bandgap conjugated system, if efficient charge transport can be realized, the theoretical minimum E loss can be 0.6 eV, while E loss of most low bandgap system usually lays in 0.8–0.9 eV 8, 9. However, in OPV, diving force is usually required and non-radiative recombination is inevitable 4, 10, 11, 12, resulting in relative large E loss. In single-junction P-N solar cell, the limit Shockley–Queisser PCE is 33%, assuming that no driving force is required for charge separation and there is non-radiative recombination during charge transport, which would lead to E loss = 0 eV. Hence, how to reduce energy loss is the key to improve the V oc of solar cell. For OPV, V OC = ( E g– E loss)/ e, where E g is the lowest optical bandgap of the donor or acceptor component and E loss is photo energy loss. The PCE of a solar cell is proportional to open-circuit voltage ( V OC), short-circuit current ( J SC) and fill faction (FF). Therefore, the general improvement of OPV performance, including both high PCE ones and moderate ones with low cost and high stability, is crucial for the commercialization of OPV. Meanwhile, for most of the reported OPV systems which exhibit PCE > 10%, the synthesis process of materials is extremely complicated and the stability of these materials is far beyond application 9. However, PCE of organic photovoltaics is still much lower than theoretical value 7, 8. In the past few years, bulk heterojunction organic photovoltaics (OPV) have achieved dramatically progress and power conversion efficiency (PCE) of single-junction OPV has reached 18.2% 1, 2, 3, 4, 5, 6. This work provides a new and general strategy to improve the OPV performance which is compatible with present optimization methods, and can be applied to improve PCE of other types of solar cells such as Perovskite and inorganic solar cells. Besides, the device also exhibits multi-functionality including transistor and phototransistors with excellent photodector performance. In this way, the performance of solar cell can be well controlled by the gate voltage of VFET and the E loss of VFEOPVs based on J71: ITIC system is dramatically reduced below 0.2 eV, significantly improving power conversion efficiency (PCE) from 10% to 18% under gate voltage of 0.9 V, which only causes negligible additional power consumption (~10 −4mJ/cm 2). Here, vertical field-effect organic photovoltaic (VFEOPV) by integrating an bulk-heterojunction (BHJ) organic photovoltaic (OPV) with vertical field effect transistor (VFET) is invented, in which VFET generates a large, uneven, internal electric field, eliminating the requirement for driving force to dissociate excitons and prevents non-radiative recombination in OPV. Generally, molecular design, morphology optimization and interfacial engineering are usually required to alleviate E loss. Limited by the inherent energy loss (E loss) in carrier transport process, the device efficiency of organic solar cells shows inferior to traditional inorganic photovoltaic devices.
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