Yehovah is one of the names of God, like Elohim, Sabaoth, Adonai, Ancient of Days...
Therefore the name Yehovah (as well as other names of God) can be applied to the Father, the Son and the Holy Spirit, Trinity consubstantial and indivisible.
See also Saint John of Damascus, "An Exact Exposition of the Orthodox Faith", book 1, chapter 12:
The Deity being incomprehensible is also assuredly nameless. Therefore since we know not His essence, let us not seek for a name for His essence. For names are explanations of actual things. But God, Who is good and brought us out of nothing into being that we might share in His goodness, and Who gave us the faculty of knowledge, not only did not impart to us His essence, but did not even grant us the knowledge of His essence. For it is impossible for nature to understand fully the supernatural. Moreover, if knowledge is of things that are, how can there be knowledge of the super-essential? Through His unspeakable goodness, then, it pleased Him to be called by names that we could understand, that we might not be altogether cut off from the knowlege of Him but should have some notion of Him, however vague. Inasmuch, then, as He is incomprehensible, He is also unnameable. But inasmuch as He is the cause of all and contains in Himself the reasons and causes of all that is, He receives names drawn from all that is, even from opposites: for example, He is called light and darkness, water and fire: in order that we may know that these are not of His essence but that He is super-essential and unnameable: but inasmuch as He is the cause of all, He receives names from all His effects.
... God then is called Mind and Reason and Spirit and Wisdom and Power, as the cause of these, and as immaterial, and maker of all, and omnipotent. And these names are common to the whole Godhead, whether affirmative or negative. And they are also used of each of the subsistences of the Holy Trinity in the very same and identical way and with their full significance. For when I think of one of the subsistences, I recognise it to be perfect God and perfect essence: but when I combine and reckon the three together, I know one perfect God. For the Godhead is not compound but in three perfect subsistences, one perfect indivisible and uncompound God.