Hybrid perovskite semiconductors are an emerging family of materials with exceptional optoelectronic properties. Solar cells of these materials have shown power conversion efficiencies greater than 25 %, light emitting diodes with external quantum efficiency >20 % and continuous wave lasers with a low lasing threshold of 6 μJ/cm2. The ‘PHOTOPEROVSKITES’ is Lethy Krishnan Jagadamma’s Marie Curie Individual Fellowship project under the supervision of Professor Ifor Samuel, funded by HORIZON 2020, European Commission [2017 September to Feb 2020].
The main tasks involved in the fellowship programme are:
- To investigate the time-resolved spectroscopic characterization of thin film perovskite solar cells
- To determine the role of crystalline grain size and grain boundaries in photophysics and photovoltaic properties of perovskite solar cells
- To develop low temperature solution-processed metal oxide interfacial charge transport layers for efficient perovskite solar cells
Publications from the PHOTOPEROVSKITES project include:
- Efficient indoor p-i-n hybrid perovskite solar cells using low temperature solution processed NiO as hole extraction layers
Lethy Krishnan Jagadamma, Oskar Blaszczyk, Muhammad T. Sajjad, Arvydas Ruseckas, Ifor D. W. Samuel; Solar Energy Materials & Solar Cells 2019 201 110071https://doi.org/10.1016/j.solmat.2019.110071https://arxiv.org/abs/1909.03838v1
We have demonstrated a low temperature (~100 °C) solution – processed and ultrathin (~6 nm) NiO nanoparticle thin films as an efficient hole extraction layers (HEL) for CH3NH3PbI3 based perovskite solar cells. We measured a power conversion efficiency (PCE) of 13.3% on rigid glass substrates and 9% on flexible substrates. Apart from the photovoltaic performance under 1 Sun, the efficient hole extraction property of NiO was demonstrated for indoor lighting as well with a PCE of 23.0% for NiO based CH3NH3PbI2.9Cl0.1 p-i-n solar cells under compact fluorescent lighting. Compared to the perovskite solar cells fabricated on PEDOT:PSS HEL, better shelf-life stability is observed for perovskite solar cells fabricated on NiO HEL.
- Interface limited hole extraction from methylammonium lead iodide films
Oskar Blaszczyk, Lethy Krishnan Jagadamma, Arvydas Ruseckas, Muhammad T. Sajjad, Yiwei Zhang, Ifor D. W. Samuel; Mater. Horiz. 2020, 7, 943
We presented a method to unambiguously distinguish between bulk and interface effects on charge extraction dynamics which is based on time-resolved photoluminescence with different excitation density profiles. We used this method to study charge extraction from solution-deposited CH3NH3PbI3 films to NiO and PEDOT:PSS layers. We found that NiO shows faster hole extraction than PEDOT:PSS from the 300 nm thick perovskite film on the time scale of 300 ps which is independent of charge carrier density in the region of 1016–1017 cm−3. This was in contrast to PEDOT:PSS where we found the charge extraction rate to be slower, decreasing with time and dependent on charge density in the region 1016–1017 cm−3 which we interpreted as charge accumulation at the interface. Hence we found that charge extraction was severely limited by the interface with PEDOT:PSS.