Emissive Charge‐Transfer States at Hybrid Inorganic/Organic Heterojunctions Enable Low Non‐Radiative Recombination and High‐Performance Photodetectors

Hybrid devices based on a heterojunction between inorganic and organic semi-conductors have offered a means to combine the advantages of both classesof materials in optoelectronic devices, but, in practice, the performance of suchdevices has often been disappointing. Here, it is demonstrated that chargegeneration in hybrid inorganic–organic heterojunctions consisting of copperthiocyanate (CuSCN) and a variety of molecular acceptors (ITIC, IT-4F, Y6,PC70BM, C70, C60) proceeds via emissive charge-transfer (CT) states analogousto those found at all-organic heterojunctions. Importantly, contrary to what hasbeen observed at previous organic–inorganic heterojunctions, the dissociationof the CT-exciton and subsequent charge separation is efficient, allowing thefabrication of planar photovoltaic devices with very low non-radiative voltagelosses (0.21 ± 0.02 V). It is shown that such low non-radiative recombinationenables the fabrication of simple and cost-effective near-IR (NIR) detectors withextremely low dark current (4 pA cm−2) and noise spectral density (3 fA Hz−1/2)at no external bias, leading to specific detectivities at NIR wavelengths of justunder 1013 Jones, close to the performance of commercial silicon photodetectors.It is believed that this work demonstrates the possibility for hybrid heterojunc-tions to exploit the unique properties of both inorganic and organic semiconduc-tors for high-performance opto-electronic devices