Degradation and outdoor performance monitoring of next generation solar cells for building integrated appliscation
Vasil Stoichkov - Thesis 2018.pdf
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This thesis focuses on the manufacturing, indoor characterisation and outdoor monitoring of Perovskite solar cells (PSCs) and Organic photovoltaics (OPVs). In order for emerging PV technologies to become commercially viable it is important that their performance under these conditions is defined. In this thesis, the outdoor performance parameters of PSCs and OPVs monitored over the course of several campaigns are reported and benchmarked against polycrystalline silicon (poly-Si) solar cells. The data has been analysed in detail against solar irradiance dose, climatic conditions and stability. It was discovered that in common with poly-Si PVs, PSCs also exhibits a distinctive negative temperature coefficient across all performance parameters (VOC, ISC, FF and PCE) which decreases with increasing irradiation dose. In all outdoor campaigns the main causes for early-life degradation were noted to be sealant failure leading to oxygen and water ingress, although longer-term degradation has been observed and assigned to photo-oxidation which in some cases was effectively suppressed by the utilisation of UV filtering. The stability of PSCs and active layers was improved by the use of luminescent down-shifting coatings which were applied as a substitute to conventional UV filters. This thesis also demonstrates the benefit of multidirectional orientation of OPVs laminated onto an industrial building prototype for building-integrated applications. It is shown that positioning OPVs to more directions than South improves the overall diurnal yield and can potentially double the energy produced per year, in particular for peak generation hours in the UK. The benefit of unreacted lead iodide as partial filter to the highly damaging UV component of sunlight is shown. The importance of a thin residue lead iodide layer in PSCs shows an improvement in the stability of fabricated devices. One of the most significant findings in this thesis is the first report on the stability of perovskite absorber layers and solar cells conducted with irradiance levels at 1sun or 100sun concentrated natural sunlight. By accelerating the aging process, this method provides invaluable information about the long-term performance of absorber layers and devices which is an immense contribution to the PV community in improving the compositions and structure of PSCs. Abstract vi The stability of 3rd generation PV remains a critical issue preventing the appearance of these new and exciting, flexible and highly efficient PVs on the market. The last part of this thesis shows the second important finding in this thesis which focuses on an in-depth study of the stability of OPVs subjected to a multi-stress accelerated lifetime testing (ALT). This study is conducted indoors which facilitates the most destructive elements to the life of an OPV exposed outdoors to be clearly determined by exposing the modules to well-defined exposure conditions.
|Goruchwylydd / Goruchwylwyr / Cynghorydd|
|Noddwyr traethodau hir|
|Dyddiad dyfarnu||Ion 2018|