Efficient intermonomer thermally activated delayed fluorescence is demonstrated for the first time, opening a new route to achieving high-efficiency solution processable polymer light-emitting device materials. External quantum efficiency (EQE) of up to 10% is achieved in a simple fully solution-processed device structure, and routes for further EQE improvement identified.

Spray‐coating is a versatile coating technique that can be used to deposit functional films over large areas at speed. Here, spray‐coating is used to fabricate inverted perovskite solar cell devices in which all of the solution‐processible layers (PEDOT:PSS, perovskite, and PCBM) are deposited by ultrasonic spray‐casting in air. Using such techniques, all‐spray‐cast devices having a champion power conversion efficiency (PCE) of 9.9% are fabricated. Such performance compares favorably with reference devices spin‐cast under a nitrogen atmosphere that has a champion PCE of 12.8%. Losses in device efficiency are ascribed to lower surface coverage and reduced uniformity of the spray‐cast perovskite layer.

We utilise spray-coating under ambient conditions to sequentially deposit compact-TiO2, mesoporous-TiO2, CH3NH3PbI(3−x)Clx perovskite and doped spiro-OMeTAD layers, creating a mesoporous standard architecture perovskite solar cell (PSC). The devices created had an average power conversion efficiency (PCE) of 9.2% and a peak PCE of 10.2%; values that compare favourably with control-devices fabricated by spin-casting that had an average efficiency of 11.4%. We show that our process can be used to create devices having an active-area of 1.5 cm2 having an independently verified efficiency of 6.6%. This work demonstrates the versatility of spray-coating as well as its potential as a method of manufacturing low-cost, large-area, efficient perovskite devices.

IntroductionPolymer solar cells based on blends of conjugated polymer donors and molecular acceptors are attracting a great deal of interest, as such systems have potential technological value due to their ease of fabrication and their relatively low production costs. While different molecular acceptors have been used in these systems, fullerene derivatives have attracted the greatest research interest. This enabled devices to be produced that have solar power conversion efficiencies approaching 6%.[1] Efficient harvesting of solar energy requires the development of polymers with high absorption coefficients and extended absorption spectra in order to enable photocurrent generation from lowerenergy photons. This in turn will require low energy-gap polymers that absorb at near-IR wavelengths. While the size of the energy gap has great importance in the design of these materials, it is also important to tailor the energy difference between the HOMO of the polymer donor and the LUMO of the fullerene acceptor in the bulk heterojunction. This energy-difference has important implications on the open-circuit voltage of devices (V OC ) with a concomitant impact on device efficiency, necessitating in many cases a trade off between energy gap of the molecular donor and the donor/acceptor HOMO-LUMO.

We explore degradation pathways within encapsulated CH 3 NH 3 PbI 3-x Cl x perovskite devices based on the inverted architecture: ITO/PEDOT:PSS/CH 3 NH 3 PbI 3-x Cl x /PC 70 BM/LiF/Al. Devices were subjected to more than 670 h of continuous illumination approximating AM1.5, with a Ts80 lifetime of (280 ± 20) hours determined. Devices stored in the dark underwent a similar drop in efficiency over the same time-period. Using external quantum efficiency, time-resolved photoluminescence, X-ray diffraction, scanning electron microscopy and laser beam induced current mapping, we attribute the primary cause of degradation to reactions with residual moisture trapped in the device, resulting in the decomposition of the perovskite. 36