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In thin‐film photovoltaics, such as organic and perovskite solar cells, charge extraction selectivity is crucial. In order to improve selectivity, charge transporting layers (doped and undoped) are frequently used; however, it is not well understood how a charge transporting layer should be designed in order to ensure efficient extraction of majority carriers while blocking minority carriers. This study clarifies how well charge transporting layers with varying majority carrier conductivities block minority carriers. The charge extraction by a linearly increasing voltage technique is used to determine the surface recombination velocity of minority carriers in model system devices with varying majority carrier conductivity in the transporting layer. The results show that transporting layers with high conductivity for majority carriers do not block minority carriers—at least not at operating voltages close to or above the built‐in voltage, due to direct bimolecular recombination across the transporting layer–absorber layer interface. Design principles are furthermore discussed and proposed to achieve selective charge extraction in thin‐film solar cells using charge transporting layers.

Abstract Continuous monitoring of food quality, blood oxygen, or industrial processes require high‐throughput near‐infrared photodetectors. Due to excellent properties like low‐cost fabrication, flexibility and narrowband response, organic photodetectors (OPDs) have a huge market potential for such applications. An organic donor–acceptor blend with a low‐energy and broad charge transfer (CT) feature is utilized, circumventing the difficulties of obtaining organic materials with significant absorption beyond 1000 nm. The increasing recombination of such low‐energy gap materials that is detrimental for the quantum efficiency is overcome by applying two photocurrent multiplication (PM) mechanisms to the donor–acceptor blend. Combined with an optical micro‐cavity, this OPD achieves a spectral response (SR) of 15 A W−1 at 1092 nm. With its spectrally narrow response of only 18 nm, this OPD technology can be used for highly resolved measurements. Contrary to OPDs working in the photovoltaic mode, this detector is optimized for operation under reverse bias. With its high spectral response, low‐cost readout circuitry like CMOS can be used for signal detection.