Chung-Yuan Kung

The passivated emitter and rear cell (PERC) concept is one of the most promising technologies for increasing crystalline silicon solar cell efficiency. Instead of using the traditional laser ablation process, this paper demonstrates spin-coated polystyrene spheres (PS) to create local openings on the rear side of PERCs. Effects of PS concentration and post-annealing temperature on PERC performance are investigated. The experimental results show that the PS are randomly distributed on wafers and no PS are joined together at a spin rate of 2000 rpm. The PS can be removed at a temperature of 350 °C, leaving holes on the passivation layers without damaging the wafer surfaces. As compared to the laser opening technique with the same contact fraction, the PS opening technique can yield a higher minority effective lifetime, a higher implied open-circuit voltage, and a slightly higher short-circuit current. Although the fill factor of the PS opening technique is lower owing to non-optimized distribution of the openings, the conversion efficiency of the devices is comparable to that of devices prepared via the laser opening process.

Transparent Zn_1−xMg_xO (x = 0.01, 0.03, and 0.05) nanocrystalline films were prepared by sol‐gel method followed by thermal annealing treatment of 700°C. Mg doping effect on the microstructural and optical properties of the Zn_1−xMg_xO films is investigated. From SEM images of all films, mean sizes of uniform spherical grains increase progressively. Pure wurtzite structure is obtained from the results of XRD. Grain sizes increase from 34.7 nm for x = 0.01 and 37.9 nm for x = 0.03 to 42.1 nm for x = 0.05 deduced from the XRD patterns. The photoluminescence spectra of the films show a strong ultraviolet emission and a weak visible light emission peak. The enhancement of ultraviolet emission and reduction of visible emission are observed due to the increase of Mg doping concentration and the corresponding decrease of oxygen vacancy defects. Besides, the characteristics of the dark/photo currents with n‐Zn_1−xMg_xO/n‐Si heterojunction are studied for photodetector application.

A low‐cost, highly reflective, liquid organic nanostructure silver conductor with superior conductivity, using back contact reflectors in amorphous silicon (a‐Si) single‐junction superstrate configuration thin‐film solar cells produced using a non‐vacuum screen printing process is proposed. The conductive paste is composed of Ag nanowires (Ag NWs) mixed with an Ag nanostructure (Ag NS) sheet. The paste is referred to as ‘Ag NWS’. A comparison of silver conductor samples with vacuum‐system‐sputtered silver samples indicated that the short‐circuit current density ( J _sc ) and the open‐circuit voltage ( V _oc ) of Ag NWS conductor cells exceeded 0.22 mA/cm ² and 66 mV, respectively. The Ag NWS conductor with back contact reflectors in solar cells was analysed using external quantum efficiency measurements to effectively enhance light‐trapping ability in a long wavelength region (580–700 nm). The cells constructed using the optimised Ag NWS demonstrated an increase of approximately 6.1% in power conversion efficiency under AM 1.5 illumination. These results indicated that the Ag NWS conductor back contact reflector layer is a suitable candidate for high‐performance a‐Si thin‐film solar cells.

We proposed a low-cost and highly reflective liquid organic sheet silver conductor using back contact reflectors in amorphous silicon (a-Si) single junction superstrate configuration thin-film solar cells produced using a nonvacuum screen printing process. A comparison of silver conductor samples with vacuum-system-sputtered silver samples indicated that the short-circuit current density (Jsc) of sheet silver conductor cells was higher than 1.25 mA/cm². Using external quantum efficiency measurements, the sheet silver conductor using back contact reflectors in cells was observed to effectively enhance the light-trapping ability in a long wavelength region (between 600 nm and 800 nm). Consequently, we achieved an optimal initial active area efficiency and module conversion efficiency of 9.02% and 6.55%, respectively, for the a-Si solar cells. The results indicated that the highly reflective sheet silver conductor back contact reflector layer prepared using a nonvacuum process is a suitable candidate for high-performance a-Si thin-film solar cells.

A novel T-shaped-gated (T-Gate) polycrystalline silicon thin-film transistor (poly-Si TFT) with vacuum gaps has been proposed and fabricated only with a simple process. The T-Gate structure is formed only by a selective undercut-etching technology of the Mo/Al bi-layers. Then, vacuum gaps are in-situ embedded in this T-Gate structure subsequent to capping the SiH4-based passivation oxide under the vacuum process chamber. Experimental results reveal that the proposed T-Gate poly-Si TFTs have excellent electrical performance, which has higher maximum on-off current ratio of 4.6 e107, and the lower off-state leakage current at VGS = -10 V and VDS = 5V of about 100 times less than that of the conventional one. It is attributed to the additional undoped offset region and the vacuum gap to reduce the maximum electric field at drain junction while ascribed to the sub-gate to maintain the on-current. Therefore, such a T-Gate poly-Si TFT is very suitable for the applications and manufacturing in active matrix liquid crystal displays (AMLCDs) and active matrix organic light emitting diodes (AMOLEDs).