Photoelectrochemical solar cell applications Essay

PHOTOELECTROCHEMICAL SOLAR CELL APPLICATIONS
Introduction
Highly efficient and most stable Photoelectrochemical (PEC) cells of various designs have been used for conversion suns energy into electrical and chimerical energies for daily use [16]. PEC is the commercially available solid state junctions used for the direct conversion of sunlight into electrical energy [78].
Photoelectrochemical (PEC) cells are mostly studied for solar and nonsolar applications. Chalcogenides of Cadmium in the form polycrystalline structure have been used in PEC cells design [9]. The highly efficient, stable of PEC cell is to be determined by, their preparation conditions, electrolytes and on experimental conditions [10].
These cells are simple in construction and have many advantages that they can be used for both electrical and chemical energy conversions. The basic requirement of a good PEC cell is thin film photo electrode having low resistivity and large grain size [11].
5.1. Solar Cell Materials
The selection of photo sensitive solar material met the following requisites.
1. it has a good absorber of the incident radiation with considerable absorption coefficient.
2. It should have a favorable direct band gap for getting maximum efficiency.
3. The purification and preparation technique should be as simple.
Above all, the material should be easily available in large quantities and nontoxic form.
The Cd1xMnxS have been studied in the present thesis have met these requirements.
This chapter deals with photoelectrochemical properties of Cd1xMnxS thin films. The effect of composition variation on the various PEC performance of present composite have been studied with special reference to opencircuit voltage (Voc), shortcircuit current (Isc), efficiency (), fill factor (ff), and flat band potential (Vfb) etc.
5.2 Preparation Procedure
The Cd1xMnxS films were deposited on ITO coated glass substrates procured from Blue star (Mumbai). The preparation method was described in section 3.4 in CHAPTER III.
5.2.1 Preparation of electrolyte
Polysulphide electrolyte solution was prepared in an aqueous medium. In order to prepare the electrolytic solutions following chemicals have been used are
(i) Sodium sulphide (Na2S)
(ii) Sulphur powder (S)
(iii) Sodium hydroxide (NaOH)
All these chemicals are 99.99 pure. One molar polysulphide electrolyte was made in double distilled water by adding proper amounts of sodium hydroxide and sodium sulphide at room temperature. The mixture was thoroughly stirred by slowly adding the sulphur powder. Prepared mixture was filtered with watmann filter paper store in a vessel which is air tightly packed. The yellowish pink colour electrolyte solution was obtained.
5.2.2 Construction of (PEC) solar cell
The present photoelectrochemical solar cell consists of three electrodes as
1. an active photoanode Cd1xMnxS thin film (11 cm2),
2. graphite as counter electrode and standard
3. reference electrode (calomel electrode (SCE)).
Redox electrolyte 1M aqueous polysulphide (NaOH + Na2S + S) solution was used. The electromagnetic source used for irradiation was tungsten lamp having 100 watt power. Present PEC cell has been prevented, from heating effect by inserting heat protecting optical instrument between the source and cell as a water lens. The photoanode and counter electrode was adjusted at distance apart 0.3 cm from each other.