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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.

Organic solar cells, despite their high power conversion efficiencies, suffer from open circuit voltage losses making them less appealing in terms of applications. Here, the authors, supported with experimental data on small molecule photovoltaic cells, relate open circuit voltage to photovoltaic gap, charge-transfer state energy, and donor-acceptor interfacial morphology.

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.

Abstract Organic phototransistors can enable many important applications such as nonvolatile memory, artificial synapses, and photodetectors in next‐generation optical communication and wearable electronics. However, it is still a challenge to achieve a big memory window (threshold voltage response ∆Vth) for phototransistors. Here, a nanographene‐based heterojunction phototransistor memory with large ∆Vth responses is reported. Exposure to low intensity light (25.7 µW cm−2) for 1 s yields a memory window of 35 V, and the threshold voltage shift is found to be larger than 140 V under continuous light illumination. The device exhibits both good photosensitivity (3.6 × 105) and memory properties including long retention time (>1.5 × 105 s), large hysteresis (45.35 V), and high endurance for voltage‐erasing and light‐programming. These findings demonstrate the high application potential of nanographenes in the field of optoelectronics. In addition, the working principle of these hybrid nanographene‐organic structured heterojunction phototransistor memory devices is described which provides new insight into the design of high‐performance organic phototransistor devices.

Photomutiplication-type organic photodetectors (PM-OPDs) are attractive for various next-generation technologies due to their lower cost, higher sensitivity and technological utility. Here, the authors report vacuum-processed narrowband PM-OPDs with enhanced sub-bandgap external quantum efficiency.

Abstract A comprehensive study of the optical properties of CsPbBr3 perovskite multiple quantum wells (MQW) with organic barrier layers is presented. Quantum confinement is observed by a blue‐shift in absorption and emission spectra with decreasing well width and agrees well with simulations of the confinement energies. A large increase of emission intensity with thinner layers is observed, with a photoluminescence quantum yield up to 32 times higher than that of bulk layers. Amplified spontaneous emission (ASE) measurements show very low thresholds down to 7.3 µJ cm−2 for a perovskite thickness of 8.7 nm, significantly lower than previously observed for CsPbBr3 thin‐films. With their increased photoluminescence efficiency and low ASE thresholds, MQW structures with CsPbBr3 are excellent candidates for high‐efficiency perovskite‐based LEDs and lasers.

The commercialisation of organic photovoltaic technology calls for research on material degradation mechanisms. Ramirez et al. show that triplet excitons produced by back charge transfer can significantly impact the photo-stability of fullerene-based devices even in the absence of water and oxygen.

The suppression of dark current in organic photodetectors (OPDs) is important for maximizing the performance of the devices. Here, the authors report the relationship between the high dark saturation current and the presence of mid-gap trap states in OPDs with a donor–acceptor structure.

Though single-material organic solar cells are attractive for next-generation photovoltaic technologies, designing new materials with ideal properties remains a challenge. Here, the authors report the use of orientation-dependent molecular electrostatics to realise efficient homojunction devices.

A steep absorption edge is preferred for high performance solar cells, but is less common for organic solar cells (OSCs). Here Panhans et al. find that the absorption tails are dominated by zero point vibrations and are responsible for the lowering of the open-circuit voltage and the performance of OSCs.

It has been commonly believed that the driving force at the donor-acceptor heterojunction is vital to efficient charge separation in organic solar cells. Here Zhong et al. show that the driving force can be as small as 0.05 eV without compromising the charge transfer rate and efficiency.

Abstract Highly responsive organic photodetectors allow a plethora of applications in fields like imaging, health, security monitoring, etc. Photomultiplication‐type organic photodetectors (PM‐OPDs) are a desirable option due to their internal amplification mechanism. However, for such devices, significant gain and low dark currents are often mutually excluded since large operation voltages often induce high shot noise. Here, a fully vacuum‐processed PM‐OPD is demonstrated using trap‐assisted electron injection in BDP‐OMe:C60 material system. By applying only −1 V, compared with the self‐powered working condition, the responsivity is increased by one order of magnitude, resulting in an outstanding specific detectivity of ≈1013 Jones. Remarkably, the superior detectivity in the near‐infrared region is stable and almost voltage‐independent up to −10 V. Compared with two photovoltaic‐type photodetectors, these PM‐OPDs exhibit the great potential to be easily integrated with state‐of‐the‐art readout electronics in terms of their high responsivity, fast response speed, and bias‐independent specific detectivity. The employed vacuum fabrication process and the easy‐to‐adapt PM‐OPD concept enable seamless upscaling of production, paving the way to a commercially relevant photodetector technology.

Strong light-matter coupling can tune exciton properties but its effect in photovoltaics remains unexplored. Here Nikolis et al. show that the photon energy loss from optical gap to open-circuit voltage can be reduced to unprecedented values by embedding organic solar cells in optical microcavities.

The performance of organic semiconductor devices depends heavily on molecular parameters. Here, Schwarze et al. point out that the molecular quadrupole moment largely influences device energy levels and show how quadrupole moments can reduce the energy barrier for charge generation in solar cells.

Molecular doping is routinely used in organic semiconductor devices nowadays, but the physics at play remains unclarified. Tietze et al. describe it as a two-step process and show it costs little, energetically, to dissociate charge transfer complexes due to energetic disorder of organic semiconductors.

Interfaces of organic donor-acceptor blends provide intermolecular charge-transfer states with red-shifted but weak absorption. By introducing an optical micro-cavity; Siegmundet al., enhance their photoresponse to achieve narrowband NIR photodetection with broad spectral tunability.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The original version of this Article contained an error in Equation 1. A factor of ‘c’ was included in the right-hand term. This has been corrected in the PDF and HTML versions of the Article.