A novel method for the measurement of diffusion lengths in solar cells
The minority carrier diffusion length in the base region of a solar cell is an important factor affecting the conversion efficiency and spectral response of the cell. Conventional methods for the measurement of minority carrier diffusion lengths in semiconductor materials are generally unsuitable for measurements on completed solar cells. This paper describes a simple and direct technique for the measurement of minority carrier diffusion length in solar cells, It has been applied to both single crystalline and polycrystalline silicon solar cells, and the results compared to standard surface photovoltage measurements.
Interpretation of steady-state surface photovoltage measurements in epitaxial semiconductor layers
Abstract Analysis of the steady-state surface photovoltage (SPV) method of measuring minority carrier diffusion length ( L ) has been extended to the case of an epitaxial layer on a thick substrate. In layers with thickness greater than four diffusion lengths, the measurement yields the bulk value of L . For layers thinner than 0.5 L , the measured value is that of the substrate. For intermediate thicknesses, the bulk value of L can be estimated. The method also provides a sensitive means of observing the influence of surface conditions on the absorption characteristics of silicon.
Study on essential drug use status and its influencing factors among cerebral infarction inpatients in county level hospitals of Anhui Province, China
Background and purpose Drug costs is one of the main components of hospitalization expenditure for cerebral infarction inpatients. In China, the National Essential Medicine System (NEMS) was created to relieve the heavy drug-cost burden for patients. The objective of this study was to investigate essential drug-use status and its influencing factors among cerebral infarction inpatients in county-level hospitals of Anhui province, China. Methods Three county-level hospitals were selected through a multi-stage cluster random sampling method. The hospitalization cost data of cerebral infarction inpatients in the three hospitals were extracted from the Anhui provincial information platform of the New Rural Cooperative Insurance System (NCMS), and whether the proportion of essential drug cost in the total drug cost reached the median value of 33.05% which was set as the evaluation index for essential drug-use status. Questionnaires for hospitals and physicians were designed and given to them to assess influencing factors. Results We retrieved the cost data of 2,189 inpatients from the NCMS platform and investigated 51 corresponding physicians in total. The drug costs accounted for 52.6% of the total hospitalization cost, and essential drug costs alone accounted for 37.0% of the total drug costs. The essential drug-cost proportion was high among physicians with a higher recognition degree on NEMS, older age, lower final academic degree, longer work experience and lower professional title. Married physicians and those with tight organizational affiliation also prescribed more essential drugs. Conclusions Increasing the proportion of essential drugs was an effective way to reduce the disease burden for cerebral infarction patients. Perfecting the NEMS, increasing government investment, reinforcing education and propaganda, and formulating relevant incentive and restrictive mechanisms were all effective ways to promote and increase the number of essential drug prescriptions written by physicians.